1. Field of the Invention
The present invention relates to a waveguide for the millimeter-wave band and the microwave band, a high-frequency circuit, and a high-frequency circuit device having the waveguide.
2. Description of the Related Art
A three-dimensional waveguide such as a hollow rectangular waveguide, which is a composite of two conductor plates, is known. For example, such a waveguide is disclosed in Japanese Unexamined Patent Application Publication No. 2002-76716 (described in paragraphs 0015 through 0017, and 0021, and shown in FIG. 1 of the cited document). The waveguide is formed by bonding two conductor plates having grooves that face each other. Additional grooves are formed at both sides of each groove to function as a choke in order to suppress electromagnetic wave leakage.
In this structure, electrical properties of the assembled waveguide are disadvantageously non-uniform due to the frequency characteristics of the chokes, which depend upon the machining accuracy of the grooves for the chokes. To obtain uniform electrical properties, high machining accuracy is required. Further, the width of the grooves for the chokes should be ¼ of the wavelength, resulting in a large waveguide. Furthermore, the disclosed document does not describe a method for bonding the two conductor plates to secure them together.